1. Field of the Invention
This invention relates to a melt-blow spinneret device. More particularly, it relates to a combined filament type, melt-blow spinneret device wherein different spinning resins are respectively and separately extruded through different spinning nozzles, followed by subjecting the extruded unstretched filaments to melt-blow spinning by a high-speed gas current. By means of the melt-blow spinneret device of the present invention, microfine combined filaments are processed into a web, non-woven fabric or molded product to be used for a mask, filter for precision filtration, battery separator, hygienic material, heat insulator, etc.
2. Description of the Related Art
The so-called melt-blow spinning wherein a thermoplastic synthetic resin is extruded through spinning nozzle plates, accompanied by spouting a high speed gas onto the extruded unstretched filaments through clearances provided on both the sides of the spinning nozzle plate, can afford microfine filaments having a diameter of e.g. 10 .mu.m or less, and also makes it possible to continuously carry out spinning and production of non-woven fabric. Hence, the above spinning is an advantageous process for producing a non-woven fabric of microfine filaments.
In recent years, a process of subjecting two different kinds of polymers to conjugate melt-blow spinning, a process of subjecting them to combined filaments type melt-blow spinning, and the like have been proposed.
As to the so-called conjugate melt-blow spinning, Japanese patent application laid-open Nos. Sho 60-99057 and Sho 60-99058 disclose a side-by-side type, conjugate melt-blow spinneret device provided with conduits for introducing two kinds of polymers from the respective extruders, into holes connected to the conduits for combining conjugate components, and an air orifice, and a spinning process using the device. These patent applications disclose that it is possible to produce microfine filaments according to a side-by-side type conjugate melt-blow spinning process, in combinations of various heterogeneous polymers such as polypropylene/polyester, polypropylene/nylon-6, etc.
In the case of the spinneret device and the production process of conjugate filaments disclosed in the above patent applications, the objective microfine filaments can be obtained by controlling the temperature, the retention time of polymers inside the extruders, the polymer compositions, etc. so that the viscosities of polymers at the time of passing through the die can be similar. However, a production of uniform conjugate filaments is possible only in the case where control of the temperature, the retention time, inside high precision extruders, the polymer compositions, etc. are possible, the retention time of polymers inside the die is short, and a die of a relatively small type is provided, without taking productivity into consideration.
Japanese patent application laid-open No. Hei 4-370210 discloses a combined filament type, melt-blow spinneret device wherein divided rooms of a first resin reservoir and a second resin reservoir are provided, and a first spinning nozzle and a second spinning nozzle obliquely bored from the bottom parts of the rooms toward tapered tip ends of the nozzles, for leading the respective spinning resins are provided. In the case of this device, the tip end width of the nozzles is specified, whereby the obliquely spun filaments are perpendicularly turned by the time of the contact of the filaments with a high speed gas current, followed by contacting with the gas current in a state where molted resins have been somewhat solidified. Hence, combined filaments spinning is possible without any fiber breakage or shot.
However, according to such a conventional device, the spinning direction of the filaments is persistently oblique, and contact of the filaments in the molten state just below the tip end of the nozzle piece, with the accompanying gas current, generated by the high speed gas current is asymmetric. Thus, a turbulent gas flow is liable to occur at the tip end part of the nozzle piece. Namely, there is raised a problem that insufficient stretching due to the turbulent gas current occurs to cause blocking between filaments, resulting in occurrence of filament aggregate. In particular, as the filament-combining ratio becomes 2/1, 3/1, etc. apart from 1/1, contact of the high speed gas current with the spun filaments of the respective components becomes non-uniform and irregular to cause blocking between the filaments of the same kind or different kinds, whereby a large quantity of filament aggregate is liable to occur.
Further, conventional apparatuses are effective only in the case where they are provided so as to carry out blow spinning in the vertical direction. Hence, the apparatuses have a drawback that the above-mentioned phenomenon becomes more notable in the case where they are provided so as to carry out blow spinning in the oblique or lateral direction.
Further, according to conventional devices, since spinning nozzles are obliquely bored in one nozzle plate block, the length of the spinning nozzles cannot help becoming larger than that of spinning nozzles bored in the vertical direction, whereby it is difficult to bore spinning nozzles with good precision and cheaply. Still further, in the case of the above devices, when they are reassembled and reused after burning, ultrasonic washing, etc. after spinning, the spinning nozzles are so long in the length direction that removal of extraneous matter adhered onto the wall thereof is liable to be insufficient, resulting in extrusion unevenness and extrusion of spiral filaments at the respective spinning nozzles, to make it difficult to spin uniform filaments. In order to solve such problems, if the spinning nozzles are shortened, the resin pressure exerted onto the spinning nozzles lowers, so that this cannot correspond to a combination of heterogeneous polymers in a broad range wherein the viscosity and the physical properties are varied. Further, there are dangers that distortion or cracks occur at the tip end part of the nozzle plate block. This becomes more notable when the nozzle plate width is broaded or the number of the spinning nozzles is increased; such a device cannot be regarded as a device taking productivity into account.
Further, according to the conventional devices, when the combining proportions of the respective components is changed, a plural number of nozzle plates corresponding to the respective combining proportions are required. Hence, a problem has been raised that an expensive device should be indispensably employed.